DESCRIPTION (Applicant's Abstract): This revised application proposes to synthesize and organize existing knowledge regarding HIV transmission through behavior change. This synthesis will be achieved through a series of five theoretically guided and methodologically rigorous meta-analyses. The first three of these meta-analyses will directly address primary prevention of HIV infection, and the last two meta-analyses will focus on the theoretical basis for risky sexual behavior: (1) A first meta-analysis will synthesize studies regarding the efficacy of risk-reduction intervention for sexual transmission of HIV; (2) A second meta-analysis will synthesize studies that focused on the efficacy of risk-reduction interventions for HIV infection among intravenous drug users (IDUs); (3) A third meta-analysis will synthesize studies that focused on the efficacy of mass media intervention for HIV risk-reduction. The investigators expect that these meta-analyses will document the effectiveness of these risk reduction strategies and identify factors related to intervention success; (4) A fourth meta-analysis will synthesize studies testing the hypothesis that intention to use condoms correlate with condom usage; and (5) The fifth meta-analysis will synthesize intervention studies and examine whether changes in intention are associated with changes in behavior. By carefully summing up the evidence to date on these important and quickly growing literatures, these meta-analyses will inform public health officials, community-based interventionists, and scientists about which interventions work best, which components of interventions have the largest impact, and the circumstances under which HIV risk-reduction interventions are most likely to be successful.